Ziplock Bag Making Machine Technical Deep Dive: Slider Applicator and Zipper Opening Mechanisms
Some ziplock bags feature a slider – a small plastic piece that rides on the zipper, making it easier to open and close. The slider applicator is an additional module that inserts the slider onto the zipper track after the zipper is attached to the film. The slider is fed from a vibrating bowl or a tape of sliders, and a pick-and-place mechanism positions it at the end of the zipper. The slider is then snapped onto the zipper by a press. The slider applicator requires precise alignment: the slider must be oriented correctly (with the opening facing the zipper) and positioned at the exact end of the zipper. The tolerance is ±0.5 mm. The applicator uses vision guidance to detect the zipper end and position the slider. The slider insertion force is controlled to avoid damaging the zipper. After insertion, the slider is often tested by an automated opener that cycles the slider to ensure smooth operation. The slider applicator operates in synchronization with the zipper attachment; it is usually placed after the zipper sealing and cooling section.
Zipper opening devices: Before the bag is sealed, the zipper must be opened (separated) to allow filling. This is done by a pair of spreading rollers or a wedge that forces the male and female tracks apart. The spreader must be precisely positioned to open the zipper without damaging the flanges. The opening force is controlled; excessive force can stretch the zipper. Some machines use a vacuum opener that lifts the top flange. The opening is performed just before the top seal is made, so that the bag opening is ready for the consumer.
Plastic Bag Making Machine
Integration with bag making: The slider applicator adds complexity and cost, but it enhances the product's premium feel. The machine's control system must coordinate the slider placement with the bag cycle. If the slider is misaligned, it may be rejected, and the bag may be discarded. The slider applicator's speed is typically lower than the rest of the machine, so it can be a bottleneck; multiple applicator heads can be used in parallel to match speed.
Maintenance: The slider applicator's pick-and-place mechanism requires regular calibration. The slider feeding system (vibratory bowl) must be kept clean to prevent jams. The slider insertion press needs periodic lubrication. The vision system's lighting must be stable. By incorporating slider applicators and opening mechanisms,
ziplock bag making machines produce premium bags that offer convenience and resealability, appealing to high-end food and consumer goods markets.
